This invention relates to an engine starter for use in starting up an internal combustion engine.
In an electromagnetic switch included in a conventional auxiliary rotary engine starter, main and auxiliary contacts are mounted for a two-step control of the motion of the starter motor at the start-up of the engine, a resistor is connected in series to the circuit formed when the auxiliary contact is closed, and the armatures of a battery and a motor are connected. On the other hand, the armatures of a battery and a motor are connected directly to the circuit formed when the main contact is closed. When the starting switch is turned on, electric current is supplied to a coil for pulling a movable member that causes the auxiliary contact to close. When the auxiliary contact is closed, electric current flows from the battery to the armature of the motor through the resistor to cause a pinion mounted on a motor axis to engage with a ring gear. Following the pinion-ring gear engagement, the main contact is closed and the starter motor rotates at a rated speed. In such an engine starter, main and auxiliary contacts are mounted on separate plungers (see, for example, Japanese Patent Laid-Open No. 07-109967, Para. 0009, FIG. 1)
Trouble with such an engine starter is that the starter itself must be large because it includes more than one plunger for driving main and auxiliary contacts separately, and it is difficult to lay out the terminals neatly. Thus, an engine starter wherein such size-reducing measure as the use of a movable contact point in common for closing and opening main and auxiliary contacts and the provision of an electromagnetic switch having a built-in resistor has been proposed (see, for example, Japanese Patent Laid-Open No. 07-174062, Para. 0009, FIG. 2).
Further, in such an electromagnetic switch wherein a coil for pulling a movable member is strengthened for the purpose of pulling the movable member more quickly, an induced counter electromotive force causing a difficulty in holding in place the movable member could generate following the release of the electromagnetic switch. A model wherein a single coil with a high impedance is used as a coil for driving a movable member and the main and auxiliary contacts are closed and opened with a time lag by connecting a resistor built-in in an electromagnetic switch in series to the auxiliary contact for supplying electric current to the armatures of the motor, as a measure for reducing induced counter electromotive force, has been proposed (see, for example, Japanese Patent Toku-hyou Laid-open 2001-508855).
In the conventional electromagnetic switch, an auxiliary contact is disposed in a contact room together with the main contact, and such an auxiliary contact is small and is given a narrow contact gap. Therefore, powders of copper generating upon the bouncing and abrasion of the movable contact point on the stationary contact points could deposit on the surfaces of the movable and stationary contact points of the auxiliary contact and could inhibit insulation, thus inducing such a trouble as a start-up failure.
The present invention has as its object the provision of an engine starter characterized by the rotation at a rated speed of the starter motor occurring after a slow engagement of the ring gear with the pinion, a wide tolerance for dimension in manufacture and the mounting of an electromagnetic switch including an auxiliary contact free from the effect of metal powders generated upon the closing and opening of the main contact.